1. Field of the Invention
The invention relates to a clamp, such as a repair clamp, comprised of thermally weldable material for a pipe also comprised of weldable material. The clamp comprises at least two segments surrounding in its position of use the pipe wherein, if needed, at least one segment has a branch pipe. The clamp has heating mats of electrically heatable conduits which are integrated into the inner surfaces of the segments. In a position of use the segments have facing border edges which can be fastened to one another by applying pressure. Each one of the two border edges of each segment has, on the one hand, at least one segment flap projecting past the border edges at least at portions thereof and, on the other hand, a pocket recessed relative to the border edges for receiving the segment flap. These segment flaps and pockets at the two neighboring bordering edges of two segments positioned adjacent to one another in the position of use provide complementary profiles. The heating mats have a corresponding contour profile comprised of at least one projecting flap which is integrated in the area of the segment flap and at least one gap in the area of the pocket of the segments.
2. Description of the Related Art
Such clamps are used in order to provide a pipe, already in use and under pressure by a medium, subsequently with a branch line. For this purpose, clamps are used which in have a branch pipe at least at one of its cylindrical segments surrounding the pipe. This branch pipe serves initially for drilling into the pipe but then also for guiding the medium into the branch line to be connected to the branch pipe. In other cases where the pipe has a defect, a clamp of segments without a branch pipe is placed onto the pipe for the purpose of repairing the pipe.
In the known clamp (DE 296 16 864) of the kind discussed above, the flaps are of a wedge-shaped design and have at their foot area a greater cross-sectional thickness than at their head area. Such flaps are stable but welding problems result, when in use, upon heating of the weldable material by heating mats. When the heating mat is positioned in the vicinity of the inner surface of the flap, the connection to the pipe is satisfactory in this area, but at the outer surface of the flap adjacent to the inner surface of the pocket no satisfactory welding connection results.
For connecting a shrink-to-fit clamp between the neighboring mantle pipes of a pipeline, a band-shaped heating mat is inserted into the gap between the mantle pipe, on the one hand, and the shrink-to-fit clamp pushed thereon (DE 37 20 577 A1) wherein the abutting ends at the end of the band of heating mat are recessed relative to one another in a stepwise manner and mesh with one another in a comb-like fashion in the position of use. The heating mat is a separate component which is placed as a loose band annularly about the mantle pipe and produces a double layer welding connection, i.e., with the circumferential surface of the mantle pipe and also with the inner surface of the shrink-to-fit clamp. Sealing problems resulting from of a clamp design comprised of at least two cylindrical segments do not occur.
In a clamp of a different kind (EP 0 438 990 A) the two segments are provided with flanges extending in the longitudinal direction which at their contact surfaces are provided with pins with different cross-sectional profiles. These pins are probably provided to prevent an undesirable rotational position of one segment relative to the other. The flanges of the two segments are pressed against one another via gliding elements with conical profiles. This requires a certain orientation of the segments. The flanges have no flaps projecting past them and no pockets for the flaps. Accordingly, the pins have no protective function.
It is an object of the present invention to develop a clamp of the aforementioned kind which provides an especially high media sealing action of its welding locations while requiring a minimal constructive expenditure and minimal heating energy.
In accordance with the present invention, this is achieved in that the segment flap has at least in areas thereof such a minimal segment flap thickness relative to the heating mat integrated into the segment flap that, when in use, the weldable material upon heating will soften and meld not only in the area of the inner contact zone between the circumferential surface of the pipe and the inner surface of the segment flap but also in the area of the outer contact zone between the outer surface of the segment flap and the inner wall of the pocket so that, after cooling, a welding connection on both sides of the segment flap results, and in that the segment flap has a uniform segment flap thickness over its entire segment flap length.
When in use, the heat produced in the heating mat integrated into the segment flap reaches the inner surface as well as the outer surface of the segment flap due to the minimal segment flap thickness, so that at these locations such high temperatures result that a welding connection on both sides of the segment flap is produced. This is especially true when the segment flap thickness is substantially uniform over the entire length of the segment flap. Even though only a single layer heating mat is used, a welding connection results not only in the contact zone between the inner surface of the segment flap and the circumference of the pipe but also in the outer contact zone between the outer surface of the segment flap and the inner wall of the pocket. Accordingly, with minimal constructive expenditure a flawless welding connection is produced also in those areas of the segments in which no heating mat is positioned, i.e., in the area of the pockets where the heating mat has gaps.
The minimal segment flap thickness produces a good radial elasticity for a deflecting movement of the segment flap upon placement of the segments onto the pipe. This is especially true for two-segment clamps wherein the two segments, viewed in cross-section, have a semi-circular profile with the segment flaps projecting therefrom. The minimal segment flap thickness requires a careful treatment of the segment flaps especially during transport and storage of the clamp.
In order to prevent a deformation of the segment flaps beyond the limits of elasticity and to thus prevent breakage of the integrated flaps of the heating mat, it is suggested according to a further development to provide at the flanges of the segments extending in the longitudinal direction protective pins which have a length that is greater than that of the segment flaps. When the segments are supported on a support surface, the segments rest on the protective pins while the segment flaps do not come into contact with the support surface and thus cannot be deformed. By providing several protective pins a xe2x80x9cbasketxe2x80x9d surrounding the projecting segment flap(s) is provided which, even when a dropped segment impacts on the ground, will protect the segment flaps against damage.
It is advantageous to use these protective pins at the same time for guiding purposes during mounting of the segments in that the pins are allowed to penetrate matching bores in the opposed flange of the neighboring segment. This provides simultaneously an ideal guiding action during mounting of the segments.
Further measures and advantages of the invention result from the following description in connection with the drawings illustrating one embodiment. The flaps and pockets shown in the drawings can be provided in any desired number.